THE GALAXY LUMINOSITY FUNCTION DURING THE REIONIZATION EPOCH
- CASA, Department of Astrophysics and Planetary Science, University of Colorado, 389-UCB, Boulder, CO 80309 (United States)
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- Astronomy Department, University of California, Santa Cruz, CA 95064 (United States)
The new Wide Field Camera 3/IR observations on the Hubble Ultra-Deep Field (HUDF) started investigating the properties of galaxies during the reionization epoch. To interpret these observations, we present a novel approach inspired by the conditional luminosity function method. We calibrate our model to observations at z = 6 and assume a non-evolving galaxy luminosity versus halo mass relation. We first compare model predictions against the luminosity function (LF) measured at z = 5 and z = 4. We then predict the LF at z {>=} 7 under the sole assumption of evolution in the underlying dark-matter halo mass function. Our model is consistent with the observed z {approx_gt} 7 galaxy number counts in the HUDF survey and suggests a possible steepening of the faint-end slope of the LF: {alpha}(z {approx_gt} 8) {approx_lt} -1.9 compared to {alpha} = -1.74 at z = 6. Although we currently see only the brightest galaxies, a hidden population of lower luminosity objects (L/L {sub *} {approx_gt} 10{sup -4}) might provide {approx_gt}75% of the total reionizing flux. Assuming escape fraction f {sub esc} {approx} 0.2, clumping factor C {approx} 5, top-heavy initial mass function (IMF), and low metallicity, galaxies below the detection limit produce complete reionization at z {approx_gt} 8. For solar metallicity and normal stellar IMF, reionization finishes at z {approx_gt} 6, but a smaller C/f {sub esc} is required for an optical depth consistent with the Wilkinson Microwave Anisotropy Probe measurement. Our model highlights that the star formation rate in sub-L {sub *} galaxies has a quasi-linear relation to dark-matter halo mass, suggesting that radiative and mechanical feedback were less effective at z {>=} 6 than today.
- OSTI ID:
- 21448910
- Journal Information:
- Astrophysical Journal Letters, Vol. 714, Issue 2; Other Information: DOI: 10.1088/2041-8205/714/2/L202; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
Similar Records
The galaxy UV luminosity function before the epoch of reionization
GALACTIC OUTFLOWS AND PHOTOIONIZATION HEATING IN THE REIONIZATION EPOCH